When using oxygen, cells produce free radicals, e.g., reactive oxygen species (ROS) and reactive nitrogen species (RNS). In our bodies, each cell produces 2.5×1011 ROS molecules per day, and human body can produce 40×1021 ROS per day. ROS not only provides and delivers life-sustaining energy, but also helps human body to eliminate bacteria and pathogens, toxins and “junks”. ROS also serve as an initiator and adjuster for various metabolisms and signal channels inside our bodies such as JNK/SAPK, P38MAPK, IKK/NF-KB, P13K, Akt, CD40/CD40L, PKC, etc, activates and regulates various transcription factors (e.g. AP-1, Nrf2, NF-KB, p53, ATF-1, HIF, HSP, SIFT-1, MST/FOXO, etc.), influences in vivo transcription and expression of various genes and participates in inflammation, immunization, reproduction, development, metabolism, cell growth, proliferation, cell regeneration, repair, and other modulations in important life processes. ROS enhances and maintains metabolism in cell, tissue and body, thereby maintaining and ensuring normal life activities.
Free radicals in human body are generated in two aspects. Firstly, they are generated from the various metabolic reactions in human body. Secondly, they arise from the exogenous free radical generated from splitting of covalent bonds resulted from high temperature, radiation, photolysis, chemical substances in the environment, such as smoking, drinking alcohol, pollution, drugs, diseases etc.
We have, inside our bodies, a dynamic antioxidant system involving, e.g. superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), which can timely and rapidly remove the excessive ROS inside the body. Under normal physiological conditions, the oxidative-antioxidant system inside our bodies maintains a homeostasis, thereby ensuring normal oxidative stress reactions and preventing ROS from damaging human bodies. Only when ROS is excessively generated and expression of antioxidant enzymes is in shortage, the balance between oxidation and antioxidation is lost and ROS is unable to be cleared timely, and cumulates in the body, thereby resulting in cellular and tissue damages (i.e., oxidative stress) and risk of human health.
ROS can directly or indirectly oxidize or damage DNA, proteins and lipids. ROS can induce gene mutation, denaturation of proteins and peroxidation of lipids, which are considered as major risk factors leading to human aging and various significant diseases, such as infertility, cataract, cancers, cardiovascular diseases, senile dementia/neurodegenerative diseases (such as Alzheimer's disease, Parkinson's disease), diabetes, inflammations (such as osteoarthritis, rheumatoid arthritis, bronchitis, etc.), infections, myocardial ischemia-reperfusion injuries, organ transplantations, atherosclerosis, etc.
Nowadays there are many “drugs for antioxidation”. However, there are few drugs that are genuinely effective in regulating oxidation-antioxidation balance.